Frequency doubling of He–Ne laser radiation at 632.8 nm

Second harmonic generation (SHG) obtained using a potassium dihydrogen phosphate (KDP) nonlinear crystal from a CW He–Ne laser as a pump source, which emits at 632.8 nm, is reported. The SHG efficiency at the power of the He–Ne laser utilized (18 mW) and the fundamental beam waist available (0.1 mm), was evaluated theoretically; the same efficiency was measured experimentally obtaining a value of (3.7–0.1)×10−7, in good agreement with theoretical predictions.